Method for preparing diarylethane

ABSTRACT

A method for preparing diarylethane is disclosed. Alkylation is carried out in a continuous type process at 100-300° C. under a pressure of 1-45 kg/cm 2  G in the presence of a solid acid catalyst while a reactant mixture comprising alpha-methylbenzylalcohol and at least one aromatic hydrocarbon at a volume ratio of 1:1-10, is fed at a weight hourly space velocity of 0.1-10 h −1 . The alpha-methylbenzylalcohol acts as an ailylating agent. Diarylethane can be prepared at a low cost, but a high production yield by the method.

This application is a 371 of PCT/KR99/00027 filed Jan. 15, 1999.

1. Technical Field

The present invention relates to a method for preparing 1,1-diarylethane(hereinafter referred to as “DAE”) at a low cost with a high yield. Moreparticularly, the present invention relates to the use ofalpha-methylbenzylalcohol (hereinafter referred to as “MBA”) inpreparing DAE in a continuous type process, whereby the production costcan be reduced, but the production yield can be enhanced.

2. Background Art

DAE, which is characteristically colorless, odorless and nontoxic, is ahigh boiling point solvent. For example, diphenylethane is 220° C. inboiling point. Particularly, phenylxylylethane (hereinafter referred toas “PXE”), which is usually used as a solvent for dissolvingwet-coloring agents for pressure-sensitive paper, is a useful compoundas a plasticizer and heat transfer oil when processing plastics. Forthese reasons, effective and economical preparation methods ofdiarylalkanes which can give good product quality, such as PXE, havebeen required.

Various methods for preparing diarylalkanes, such as PXE, have been wellknown to the art. Of them, general is the reaction of alkyl benzenefractions containing 6-9 carbon atoms in the presence of a catalyst withstyrene acting as an alkylating agent. Based on the catalyst employed,this technique is classified largely into the following two categories.

A first technique is to use conc. sulfuric acid as a catalyst, asdisclosed in Japanese Pat. Laid-Open Pub. Nos. Hei 4-257530 and Sho48-97858. This technique has an advantage of yielding relatively highquality products, but allows production processes in batch type only,because sulfuric acid is a homogeneous catalyst. Further, sulfuric acidrequires a facility for isolating reaction products from the homogeneouscatalyst and extorts after-treatments, such as acid neutralization andwashing. Furthermore, use of sulfuric acid leaves problems to be solvedin practice, including facility corrosion and waste water pollution.

In order to restrain the side reaction in which styrene monomers areconverted into styrene oligomers, a large molar ratio of the styrene ismonomers to the aromatic hydrocarbons, for example, 1:10 is needed whenusing the homogeneous catalyst. In addition, the catalyst should be fedat a weight as twice as that of styrene. The use of a large amount ofthe catalyst is disadvantageous in many aspects, for example, a reactorwith a large volume and an increase in reclaim cost, so that thetechnique using sulfuric acid is inadequate to mass-production.

A second technique is as described in Japanese Pat. Laid-Open Pub. Nos.Sho 49-31652 and 63-238028, characteristic of using heterogeneous solidacid catalysts. The technique of using heterogeneous solid acidcatalysts to react styrene with alkyl benzene has neither difficulty incatalyst isolation nor the problem of facility corrosion. However, itshows low production yield comparing to the techniques using homogeneouscatalysts. Further, the second technique should be operated at a lowstyrene ratio because of side-products such as styrene oligomers.Examples of the heterogeneous solid acid catalysts include Y-typezeolite (Japanese Pat. Laid-Open Pub. No. Sho 63-238028) and active clay(Japanese Pat. Laid-Open Pub. No. Sho 49-31652). However, these twoprior arts are of batch type. A continuous type process is also known asdisclosed in Japanese Pat. Laid-Open Pub. No. Sho 62-42938 which uses acation exchange membrane as a solid acid catalyst, but nowhere ismentioned catalyst life.

In result, upon preparing DAE by the alkylation of aromatichydrocarbons, conventional techniques in which to use styrene as analkylating agent are difficult to carry out in a continuous type processand have difficulty in using solid acid catalysts, even if they areconvenient to isolate and reclaim, because of the production of a largequantity of styrene oligomers and of the low production yield ascribedto a low styrene fraction in the reaction. Use of sulfuric acid as acatalyst with the aim of obtaining a high production yield may causefacility corrosion and environmental pollution, so thatcorrosion-resistant facilities and an additional acid waste treatmentprocess are required.

DISCLOSURE OF THE INVENTION

The intensive and thorough research on a method for preparing DAE,repeated by the inventors, resulted in the finding that use of MBA as analkylating agent in the presence of a solid acid catalyst selected fromsynthetic or natural zeolites, such as Y type zeolite, X type zeolite,zeolite β, modernite, L type zeolite, ZSM-5, ZSM-11, ZSM-18, ZSM-12,mazzite and offretite, MCM-41, KIT-1, KIT-2, AIKIT-3, clay, andsilica-alumina, can enhance the production yield of and the selectivityfor DAE and allow the overall reaction process to be executed in acontinuous process as well as a batch process.

It was also found that, when DAE was prepared on the basis of the aboveresearch, the conversion of MBA and the selectivity for DAE are bothhigh even under the condition of high mole fraction of MBA in reactionmaterials and that the operability of the preparation in a continuousreactor significantly reduces the production cost.

The present invention is based on the above findings.

Therefore, it is an object of the present invention to overcome theabove problems encountered in prior arts and to provide a method forpreparing DAE at a high conversion rate and production yield witheconomical favorableness.

In accordance with the present invention, the above object could beaccomplished by a provision of a method for preparing DAE, in whichalkylation is carried out at a temperature of 100-300° C. under areaction pressure of 1-45 kg/cm² G in the presence of a solid acidcatalyst while a reactant mixture comprising alpha-methylbenzylalcoholas an alkylating agent and at least one aromatic hydrocarbon at a volumeratio of 1:1-0, is fed at a weight hourly space velocity of 0.1-10 h⁻¹.

In accordance with one aspect of the present invention, the solid acidcatalyst is selected from the group consisting of Y type zeolite, X typezeolite, zeolite beta(β), modernite, L type zeolite, ZSM-5, ZSM-11,ZSM-18, ZSM-12, mazzite, offretite, MCM-41, KIT-1, KIT-2, AIKIT-3, clay,and silica-alumina.

BEST MODES FOR CARRYING OUT THE INVENTION

The present invention is characterized in that MBA, instead of styrene,is used as an alkylating agent. As a result of the intensive andextensive research of the inventors, the novel alkylating agent wasobserved to be much more advantageous in an economical aspect than theconventional one. MBA is an intermediate in the process of producingstyrene monomers and can be obtained by oxidizing ethyl benzene. Noparticular limits are levied on the purity of MBA and the MBA whichcontains acetophenone at an amount of 15% may be used.

In the present invention, DAB is prepared from aromatic hydrocarbonswith MBA serving as an alkylating agent. Examples of the aromatichydrocarbons available include one or more selected from the groupconsisting of benzene, toluene, ortho-xylene, meta-xylene, para-xylene,ethyl benzene and trimethyl benzene. No particular limits are levied onthe conditions of aromatic hydrocarbons, such as purity. Particularlypreferable are aromatic hydrocarbon individuals isolated from therefomates when executing conventional petrochemical processes, or themixtures thereof.

In accordance with the present invention, a useful catalyst is a kind ofa solid acid catalyst selected from the group consisting of zeolites,for example, Y type zeolite, X type zeolite, zeolite beta (Higgins, etal., Zeolites Vol. 8, 1988, p446), modernite, L type zeolite, ZSM-5(U.S. Pat. No. 3,702,886), ZSM-11 (Fyfe, et al., J. Am. Chem. Soc. vol.111, 1989, p2470), ZSM-18 (Lawton, et al., Science, vol. 247, 1990,p1319), ZSM-12 (LaPierre, et al., Zeolites, vol. 5, 1985, p346), mazzite(D. W. Breck and G. W. Skeels, U.S. Pat. No. 4,503,023, 1985) andoffretite (D. W. Breck, Zeolites Molecular Sieves, Wiley, 1974, p103),MCM-41, KIT-1, KIT-2, AIKIT-3, clay, and silica-alumina. Theseexemplified solid acid catalysts may be used as powder or in a moldedform. As for the Y type zeolite, X type zeolite and modernite catalysts,they may be natural or synthesized. MCM-41, KIT-1, KIT-2 and AIKIT-3,available in the present invention, are mesoporous molecular sieves.KIT-1 is structured to have channels interconnecting in a threedimensional disordered way. The MCM-41 used in the present invention wasprepared on the basis of the content of J. Am. Chem. Soc, 1992, vol.115., p 10834, to Beck et al. and Preparation Example I disclosed inKorean Pat. Appl'n No. 97-41469 filed by the applicant. KIT-1 wasprepared in the way disclosed in Example I of Korean Pat. Appl'n No.96-52841 filed by the applicant while KIT-2 was prepared according toExample IV of the same patent application. AlKIT-3 was prepared in theway described in Example IX of Korean-Pat. Appl'n No. 97-6051 filed bythe applicant. Where the catalyst has a form, alumina or silica may beadded at an amount of 10-80 weight % upon molding. No restraint residesin the shape of the catalyst.

Now, a description will be given of the reaction conditions under whichDAE is prepared by the alkylation of aromatic hydrocarbons with MBA inthe presence of the catalyst, below.

Temperatures for the reaction may be varied depending on otherconditions, but preferably ranges from 100 to 300° C. and morepreferably from 120 to 270° C. For example, if the reaction is carriedout at a temperature higher than 300° C., a serious side-reactionattributable to the self-reaction of MBA occurs and much coke isproduced, leading to the reduction of catalyst life span and thedecrease of production yield. On the other hand, at a temperature lowerthan 100° C., it is difficult for the alkylation to occur. Prior to thealkylation, the catalyst is preferably dried in an inert gas atmosphere.100-120° C. is suitable for drying the catalyst.

As for reaction pressure, it is on the order of 1-45 kg/cm² G andpreferably 2-40 kg/cm² G. Higher pressures than 45 kg/cm² G causes aserious side reaction ascribed to the self-reaction of MBA. On the otherhand, lower pressures than 1 kg/cm² G makes it difficult to execute thealkylation in a continuous manner in an immobilized bed reactor. The gassuitable for maintaining the reaction pressure is selected from argon(Ar), nitrogen (N₂), hydrogen (H)₂ and the mixtures thereof and thereare no particular limits on the condition for the gas, such as purity.

In the reactant mixture used, the volume ratio of the aromatichydrocarbons to the alkylating agent, that is, MBA, is on the order of1-10:1 and preferably 2-8:1. For example, if the volume ratio is largerthan 10, the production yield of PXE decreases. On the other hand, thevolume ratio lower than 1 causes coke to occur on the catalyst,resulting in the reduction of catalyst life span and the decrease ofproduction yield.

As for the weight hourly space velocity (h⁻¹) of the reactant mixture ofMBA and aromatic hydrocarbons, it ranges from 1 to 10 and preferablyfrom 2 to 8.

A better understanding of the present invention may be obtained in lightof the following examples which are set forth to illustrate, but are notto be construed to limit the present invention.

EXAMPLE 1

30 g of pelletized H-Beta (CP-811-BL25, commercially available from PQ)was charged into a 316 stainless steel fixed bed reactor (550 mm×50 mmOD). The reactor was heated to 110° C. under 0.20 SLPM (standard literper minute) Argon flow at a pressure of 2 kg/cm² G. A mixture ofxylene:MBA=5:1 was used as a reactant feed.

After drying the catalyst, argon was fed at a velocity of 0.20 SLPM toform a pressure of 20 kg/cm² at a temperature of 200° C. and, under thiscondition, reaction was carried out as feeding the reactant mixture at aweight hourly space velocity of 4.5 h⁻¹.

After 40 hour reaction, the product was analyzed by gas chromatographyequipped with a flame ionization detector. The analysis showed that theaverage conversion of MBA was 100.0% and the average production yield ofPXE was 86.21 wt %.

The conversion of MBA and the selectivity for PXE were calculatedaccording to the following Equations 1 and 2, respectively:$\begin{matrix}{{{Conversion}\quad (\%)\quad {of}\quad {MBA}} = {\frac{{Weight}\quad {of}\quad {MBA}\quad {reacted}}{{Weight}\quad {of}\quad {MBA}\quad {used}} \times 100}} & \left\lbrack {{Equation}\quad 1} \right\rbrack\end{matrix}$

$\begin{matrix}{{{Selectivity}\quad (\%)\quad {for}\quad {PXE}} = {\frac{{{Wt}.\quad {of}}\quad {PXE}\quad {converted}\quad {from}\quad {MBA}}{\begin{matrix}{{{{Wt}.\quad {of}}\quad {all}\quad {products}}\quad} \\{{converted}\quad {from}\quad {MBA}\quad {reacted}}\end{matrix}} \times 100}} & \left\lbrack {{Equation}\quad 2} \right\rbrack\end{matrix}$

EXAMPLE 2

The same procedure as that of Example 1 was repeated, except that thesilica-alumina (commercially available from Aldrich) extruded to pelletforms in a well known process was used as a catalyst for 250 hours. Gaschromatography analysis showed that the conversion rate of MBA was100.0% and the selectivity for PXE was 68.04 wt %.

EXAMPLES 3 TO 6

The same procedure as that of Example 1 was repeated, except thatNa-Beta (commercially available from PQ), Y type zeolite (CBV-780,commercially available from PQ), X type zeolite (molecular sieves, 13X,commercially available from Aldrich), and KIT-1, all extruded to form ⅛″as pellet, were each used as a catalyst. The analysis results are givenas shown in Table 1, below.

TABLE 1 MBA Conversion PXE Selectivity Examples Catalysts (%) (%)Example 3 Na-Beta 99.1 81.1 Example 4 Y 99.9 62.5 Example 5 X 100 57.6Example 6 KIT-1 100 61.4

EXAMPLE 7

The same procedure as that of Example 1 was repeated, except that areactant mixture of xylene and MBA containing 10% acetophenone wasreacted for 100 hours in the presence of a modernite catalyst extrudedwith the aid of 20% alumina. Analysis showed that the MBA conversion andthe PXE selectivity were 100.0% and 78.3 wt %, respectively, on theaverage.

COMPARATIVE EXAMPLES 1 TO 6

To a 250 ml autoclave containing 100 ml of para-xylene, a homogeneouscatalyst (AlCl₃, SiCl₄) or a heterogeneous active clay was added as muchas 50 wt % of styrene. Reaction was executed for predetermined timeswith dropwise addition of styrene. The catalysts used, the reactionconditions and the PXE selectivity are given in Table 2, below.

TABLE 2 PXE Comparative Rxn. Temp. Rxn. Time Selectivity ExamplesCatalysts (° C.) (hour) (%) C. Examp. 1 AlCl₃ 25 20 0 C. Examp. 2 SiCl₄25 20 0 C. Examp. 3 Active Clay A 25 20 0 C. Examp. 4 Active clay B 2520 0 C. Examp. 5 Active clay A 60 5 20 C. Examp. 6 Active clay B 80 3 80

Industrial Applicability

As described hereinbefore, the method according to the present inventionenables DAE to be prepared at a low cost in a high production yield, sothat it is applicable to commercial processes.

The present invention has been described in an illustrative manner, andit is to be understood the terminology used is intended to be in thenature of description rather than of limitation. Many modifications andvariations of the present invention are possible in light of the aboveteachings. Therefore, it is to be understood that within the scope ofthe appended claims, the invention may be practiced otherwise than asspecifically described.

What is claimed is:
 1. A method for preparing 1,1-diarylethane, whichcomprises conducting an alkation reaction in a continuous type processat a temperature of 100-300° C. under a reaction pressure of 1-45 kg/cm²G in the presence of a solid acid catalyst while a reactant mixturecomprising alpha-methylenzylalcohol and at least one aromatichydrocarbon at a volume ratio of 1:1-10, is fed at a weight hourly spacevelocity of 0.1-10 h⁻¹, said alpha-methylbenzylalcohol acting as analkylating agent.
 2. A method as set forth in claim 1, wherein saidaromatic hydrocarbon is selected from the group consisting of benzene,toluene, ortho-xylene, meta-xylene, para-xylene, ethyl benzene,trimethyl benzene and the mixtures thereof.
 3. A method as set forth inclaim 1, wherein said solid acid catalyst is selected from the groupconsisting of Y type zeolite, X type zeolite, zeolite beta(β),modernite, L type zeolite, ZSM-5, ZSM- 11, ZSM- 18, ZSM-12, mazzite,offretite, MCM-41, KIT-1, KIT-2, AIKIT-3, clay, and silica-alumina.
 4. Amethod as set forth in claim 1, wherein said alkylation is carried outat a temperature of 120-270° C.
 5. A method an set forth in claim 1,wherein said reaction pressure is on the order of 2-40 kg/cm² G and ismaintained by feeding a gas selected from the group consisting of argon(Ar), nitrogen (N₂) and hydrogen (H₂) and the mixtures thereof.
 6. Amethod as set forth in claim 1, wherein said reactant mixture comprisesalpha-methylbenzylalcohol and at least one aromatic hydrocarbon at avolume ratio of 1:2-8.
 7. A method as set forth in claim 1, wherein saidreactant mixture is fed at a weight hourly space velocity of 2-8 h⁻¹.